The present invention relates to a device for feeding gases, aerosols and/or mixtures of gases and solids into the combustion of a steam boiler or other combustion chambers using heat, and a process for diminishing pollutants, which are formed when burning gases, aerosols and/or mixtures of gases and solids in steam boilers or other combustion chambers using heat.
Usually a waste gas containing a nitrogen compound is disposed of in a two-stage combustion chamber, the first chamber operating with a certain amount of oxygen removed and the second one with a corresponding amount of oxygen added. In addition a heat exchanger is positioned between the two combustion chambers, to minimise the thermal production of NO.sub.x. Plants having two-stage combustion are known from R. Romer, W. Leukel, A. Stoeckel and G. Hemmer's "Effect of producing nitrogen oxide from nitrogen bonded with fuel using combustion methods, Chem.-Ing.-Techn. MS 875/81" or O. Carlowitz, H. Wiebe and U. Gravemeier's "Combustion of vapours containing ammonia and nitrogen oxide in a spin combustion chamber system, VDI-Reports No. 423/81".
These combustion plants are primarily used for reducing harmful substances, whereby there is a considerably smaller amount of flue gas than with combustion processes in power stations. Adding a combustion chamber, which is operated with a deficiency of air, to a steam boiler with forced circulation is ruled out due to the altered heat release and consequent change in the local heat exchange.
The amount of NO.sub.x emitted can be decreased by using suitable burners. There are zones within the burner flame which are produced by feeding specific amounts of air and fuel, and which have a deficiency of air and corresponding amount of CO, which in turn reduces the NO.sub.x. These burners are more effective if oxygen-enriched combustion air, which is mainly available as a mixture of fresh air and recycled flue gas, is added at a suitable place, reducing the flame temperature as well as the oxygen supply.
Furthermore, it is known from VDI-Reports No. 574, pages 443 ff, that to minimise the NO.sub.x content in flue gas, fuel containing nitrogen is used in combustion plants with burners, to modify the fuel concentration and air mass to the individual burners.
These methods can only be used with low volumetric rates of the waste gas flow which contains nitrogen compounds. This waste gas should be fed in the direct region of the flame, otherwise it will not mix at all or at most very insubstantially with the reducing agent.